A candidate is asked to draw the graph of y=x2+6x−27 and a linear graph on the same axes such that their intersections give the solutions of x2+5x−29=0. What is the equation of the linear graph?
Worked solution (try it first)
Setting the curve equal to the line must give the same equation as x2+5x−29=0.
Subtract the equation from the curve: (x2+6x−27)−(x2+5x−29)=x+2.